Recently, a very well regarded prelate of the Church — whom I happen really to believe to be a very good and holy man — tweeted about the Moderna coronavirus vaccine. He wrote that vaccine "is not morally produced," owing to the use in some phases of its production of biological specimens obtained originally through abortion. He "urge[s] all who believe in the sanctity of life to reject" this or any vaccine produced using such technologies. Now, I'm no bioethical expert. However, I do try to follow the guidance of such experts, like the theologians and philosophers at the National Catholic Bioethics Center, who have offered a statement on the subject. I depend upon Church teaching, like the Pontifical Academy for Life's 2005 statement "Moral Reflections on Vaccines Prepared from Cells Derived from Aborted Human Foetuses" and the Catholic Medical Association's statement "Vaccines Prepared from Cells Derived from Aborted Human Fetuses ." And the relevant guidance of such experts indicates that this is a more complex subject than the good bishop’s tweet would suggest. The first flaw is the medium. It takes more than 280 characters to provide even a cursory comment on this issue with the necessary qualifications and allowances. This demands nuance and narrowness on the one hand, while at the same time a certain amount of liberality on the other hand. A tweet cannot do this. In a similar way, one prominent Catholic writer’s ALL CAPS remark on Facebook — that he “WON'T GET A VACCINE MADE FROM ABORTED CHILDREN FOR THE SAME REASON THAT I WON'T BUY A LAMPSHADE MADE OF HUMAN SKIN” — can only be said in all charity to be wanting in depth and precision. When the bishop says of Moderna's vaccine that, "unborn children died in abortions and then their bodies were used as 'laboratory specimens'," certain details are omitted that really seem relevant to informing moral decisions. One might easily come away imagining that an unborn child was directly killed with a view to developing this drug. But the truth is rather more complex. It does seem that both Moderna and Pfizer relied in the manufacture of their vaccines on cell lines which are "immortalized" clones of cells originally taken from the kidney of an aborted fetus in the 1970s. It is important to note, however, that this reliance is upon knowledge obtained from former tests on the nature of the virus, and these cells are not actual “components” of either vaccine. Further, these cells are not the original biological cells that were in the actual fetus's body, and they've also been significantly altered. Furthermore, these cells do not constitute a "part" of the vaccine. There are no aborted baby cells in the vial from which a patient's dose is drawn. Mark well, there’s still an ethical problem here. It is morally repugnant that these cells were derived from experimentation on the kidney cells of a nameless murdered child of God, however long ago. Their continued use is offensive and disturbing. We can and should rightly protest against it, and ask that these cells be retired from use. However, there is a material separation between the original morally offensive act(s) and the production of the vaccines, and an even further removal between the original act and a patient's choice in getting the vaccine. We would do well to recall the principles of moral cooperation as delineated in moral theology. Moral cooperation with an act can be immediate or remote, and it can be material and/or formal. Suppose John hires a hitman to kill his ex-wife, and gives him the gun to do it. He has formally participated (willing the evil action). and materially cooperated (by providing the gun and payment). His cooperation is immediate, because he instigated the evil action. The only person whose cooperation is less remote is the guy who pulled the trigger. But suppose John’s a gun manufacturer, who makes guns for hunting and sport. Some random other person uses one of his guns to kill his ex-wife. John is remotely and materially cooperating, but not formally cooperating.